1. Field of the Invention
The present invention relates to an electrical terminal and more particularly to an electrical terminal and housing for use with a surge protection cartridge which is simple, reliable and economical.
2. Description of the Related Art
Surge protection cartridges or modules may be used with modular terminal block assemblies in telecommunication networks as shown and described, for example, in U.S. Pat. Nos. 5,627,721; 5,779,504 and 6,243,250. The surge protection cartridge includes over-voltage/over-current protection devices to protect telecommunication networks from malfunctions and the users of the networks from injury, due to high voltage/high current surges. An important principal of electrical protection is to provide a low impedance path to ground for undesirable or foreign voltages, such as those created by lightning. On a telephone line circuit, current flows into the telephone equipment on the tip lead and returns on the ring lead. Voltage is applied to the telephone line so that the current will flow through the telephone equipment. When the voltage on the line at the protection device raises above a preset level, usually 200-600 volts, a change of state in the protection device occurs and the current flows to ground while the undesirable high voltage is maintained. When high current flows through the contact interface of the protection device and the tip terminal, an electromagnetic force, which is referred to as xe2x80x9crepulsion forcexe2x80x9d or xe2x80x9cblow-offxe2x80x9d, may create a gap at the contact interface. Consequently, electrical arcing may occur and erode the contact surface, and/or weld surfaces together or create a high resistance, or result in an open circuit causing a network malfunction.
An existing tip clip design that has not proven effective is shown in FIGS. 1 and 2. The design is of a tip terminal or clip 10 having a first electrical contact 12, a second electrical contact 14 and a bridge 16. At each end of the tip clip is a connector barb, a right barb 18 and a left barb 20.
The second electrical contact 14 includes a base portion 22, two converging arm portions 24, 26, a contact region 28 and flare portions 29, 30. The width of each arm portion, from a left surface 31 to a right surface 32, is 0.080 inches and the distance from a bottom surface 34 of the base 22 to the contact region is 0.227 inches. The length of the two arms from the base is 0.314 inches. The distance across from arm to arm at its greatest extent is 0.180 inches. The thickness of each arm is 0.020 inches and the material of the clip is Olin Brass C510 phosphor bronze. The clip is plated with electro tin (150-200 micro inches) over nickel (50-100 micro inches) which in turn is plated over copper flash (30-50 micro inches). As seen in FIG. 2, the width of the rounded opening of the contact region is 0.030 inches and the gap between the arms at the contact region is 0.004 inches. The spring constant of the tip clip is 0.073 lb./mil. The diameter of a protection device lead is 0.039 plus or minus 0.001 inches. When such a lead is inserted into the clip, the deformation of the clip is between 0.003-0.006 inches. At these deformations, the contact normal force is 0.45-0.9 pounds.
When the tip clip shown in FIGS. 1 and 2 was tested by exposure to a 10 kA current surge test, there was arcing and physical damage in the contact region.
The difficulties encountered with the previous tip clip have been overcome by the present invention. What is described here is an electrical terminal for a surge protection cartridge used with a standard telecommunication frame, said terminal for receiving a lead of an existing surge protection device and comprising a metal element having a first contact portion, a second contact portion and a spanning portion connecting the first and the second contact portions, the second contact portion including a base and first and second arms extending away from the base, the arms being generally parallel to one another along first portions of the arms, the arms converging toward one another along second portions of the arms, and the arms being flared away from one another along third portions of the arms.
There are a number of advantages, features and objects achieved with the current invention which are believed not to be available in earlier related devices. For example, one advantage is that the present invention provides an electrical terminal or tip clip which is simple, effective and economical. Another object of the present invention is to provide a tip clip with increased normal force at the region of contact with a lead to enhance that contact. Another object of the present invention is to provide a tip clip which does not exhibit arcing and physical damage when exposed to a 10 kA current surge test; the surge does not destroy the electrical contact and the terminal continues to function after the surge event.
A more complete understanding of the present invention, and other objects advantages and features thereof will be gained from a consideration of the following description of the preferred embodiment read in conjunction with the accompanying drawing provided herein. The preferred embodiment represents an example of the invention which is described here in compliance with Title 35 U.S.C. xc2xa7 112 (1st paragraph).